A study finally proves exactly “when” to eat before exercising to maximize weight loss & better behaved fat cells.

If you are like me, you want to get the most bang for your exercise buck because the rest of the day you have plenty to do and often much of it involves sitting. So I’ve often wondered, as I am sure you have, too, how to maximize the two E’s, exercise and eating. Would we lose more weight if we ate breakfast and then worked out a bit later? Should we have a green drink before we get into the car to drive down to the lake? Or would we lose more weight if we hit the gym first thing in the morning on an empty stomach, continuing the fast from the night before?

Some health gurus say if you don’t eat breakfast you’re training your body to become diabetic. Is this true? Are these health mentors exercisers themselves? Not everyone works out regularly, so comments from folks who don’t are always a bit suspect to me.

I work out daily. Perhaps you work out several days a week. Or maybe you walk half an hour or an hour a day and are hoping to keep those love handles to a minimum. We all want to know what’s the best way to eat and then work out that keeps those extra fats cells on our thighs or waist or under our armpits banned to a distant universe far, far away.

There is also the issue of “good” and “bad” fat. Bad fat gives off nasty molecules of inflammation that can travel throughout your body causing havoc wherever they roam. For example, inflammatory molecules that might originate from inside your gut, may travel through the blood and get inside your brain. This can cause brain fog, migraines or fatigue. Good fat does the opposite. It reduces inflammation. So we all hope that by our exercise efforts, our fats cells are being trained to behave healthier and less inflammatory and less damaging all throughout us.

So is there a specific timing of eating in proximity to exercising that helps us stay thinner, healthier, and less inflamed? Finally a study hot off the British press answers these questions head on. I am excited to share this with you.

Researchers from the University of Bath in the U. K. took a group of overweight men. They had them walk for an hour on an empty stomach or two hours after consuming a high-calorie breakfast that was also high in carbs. Blood and fat samples were collected before working out and one hour later.

What was so unique and helpful for you and me was that these researchers looked at the effects of eating and working out on genes— genes that rule how fat cells behave.

They looked at two genes, PDK4 and HSL. These genes turn “on” or are “expressed” when your extra stored fat cells are used as fuel (for metabolism) when you push your body during your work out or even as your stroll for half an hour. This means you are burning fat instead of the carbohydrates from your recent meal. When these genes are turned on they also train fat cells to behave healthier (less pro-inflammatory).

Gene expression of these two genes inside fat cells increased when the men fasted and then exercised. They decreased when they ate before exercising.

This study showed for the first time that within several hours of eating your stored fat is busy responding to the meal. If you work out within a few hours or immediately after eating, your exercise efforts don’t stimulate the release, removal or other health benefits on your fat cell dynamics.

If instead you exercise in a fasting state, such as first thing in the morning or 4 to 5 hours since you last ate, you lose more weight and your fat cells are better behaved (promote less inflammation versus more).

This study answers the genetic question of “to eat or not to eat” before or after you work out. This may be why you have been “hitting” the gym but not losing weight because it was within two hours of when you last ate. This study puts the big “aha” into our understanding about getting more benefits from our exercise efforts.

Thank you to the University of Bath!

This is the first study to show that feeding prior to acute exercise affects post-exercise adipose tissue gene expression. The authors concluded that eating blunts fat cell adaptation to regular exercise for “up to several hours” after you’ve finished chewing and swallowing.

Moral of this story: have your cup of Joe or water with lemon, go work out, and then eat. This gives you the most workout benefits and keeps you leaner. If you work out at night, don’t eat your dinner till after your workout. Be well. Be smart. Knowledge is power.

Dr. B.


Am J Physiol Endocrinol Metab. 2017 Mar 14:ajpendo.00006.2017. doi: 10.1152/ajpendo.00006.2017. Feeding Influences Adipose Tissue Responses To Exercise In Overweight Men.